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Back Exam IV

# Back Exam IV - BACK EXAM IV PRICE 1 Given the table of...

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BACK EXAM IV – PRICE 1. Given the table of thermodynamic data for the reaction: B 2 O 3 (s) + 6 HF (g) Æ 2 BF 3 (g) + 3 H 2 O (l), answer the questions that follow. B 2 O 3 (s) HF (g) BF 3 (g) H 2 O (l) Δ H o f (kJ/mol) –1273 –271 –1137 –286 S o (J/mol.K) +54 +174 +254 +70. (a) Is this an exothermic or an endothermic reaction? (b) Is the entropy change for this reaction positive or negative? (c) Calculate Δ S o surr at a temperature of 25 o C. (d) Based upon your answers to questions (a) , (b) , and (c) , what can you say about the spontaneity of the reaction at 25 o C? (e) Show that the reaction is non-spontaneous at a temperature of 350 o C. (f) Will increasing the temperature above 350 o C make this reaction spontaneous? Explain. (g) What is the range of temperatures for which this reaction is spontaneous?

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2. There are two forms of tin: White powdery Sn, Δ G o f = 0 kJ/mol; Grey metal Sn, Δ G o f = +0.13 kJ/mol (a) Which form is the most thermodynamically stable form of tin? Why? (b) Calculate Δ G o rxn for Grey Sn Æ White Sn, and explain why this reaction is not observed, i.e., why tin cans and cups do not suddenly turn into tin powder.
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Back Exam IV - BACK EXAM IV PRICE 1 Given the table of...

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